The method of choice to reveal the conformation of protein molecules in atomic detail has been X-ray single-crystal analysis. Since the first structural analysis of diffraction patterns, computer calculations have been an important tool in these studies (Blundell & Johnson, 1976). As is described by Sheldrick (1985), it has been taken for granted that a necessary first step in the determination of a protein structure would be writing computer programs to fit structure factors. In contrast the combined use of the structural analysis of NMR data and computer calculations has been quite limited. An early attempt of such structural calculations was the quantitative determination of mononucleotide conformations in solution using lanthanide ion shifts (Barry et al. 1971).

An exciting aspect of NMR spectroscopy is its ability to monitor, non-invasively, a variety of small molecules in cells and tissues. This leads to the possibility of investigating details of cellular biochemistry previously obscured by separation and purification procedures.

A survey of magnetic resonance imaging techniques is presented. Emphasis is put on the basic types of measurement procedures rather than, discussing all variants proposed so far. The general experimental procedure consists of two phases, the preconditioning period and the image formation period. While the preconditioning period determines the image contrast, the image formation process is responsible for image resolution. Means to improve sensitivity and to minimize measurement time are discussed.

In the very short time since magnetic resonance imaging (MRI) was born it has gained surprisingly rapid and enthusiastic acceptance and has speedily proliferated, particularly in the United States and Western Europe. Magnetic resonance imaging (MRI) has successfully challenged computed tomography (CT) in all areas of the body where respiratory motion does not degrade the image (Steinberg, 1986). Newer techniques using a multiplicity of approaches are starting to close the gap between CT and MRI, even in the upper abdomen where the effects of respiratory motion are most pronounced. Although MR is already widely clinically applied and is an accepted everyday diagnostic modality in most large medical centres in the United States, it is not a mature modality. It is rapidly evolving, with whole new areas opening to investigation which will vastly broaden its applications.